Modifiers

Request Header

Couper offers three attributes to manipulate the request header fields. The header attributes can be defined unordered within the configuration file but will be executed ordered as follows:

Modifier	Contexts	Description
`remove_request_headers`	Endpoint Block, Proxy Block, Backend Block, Error Handler	List of request header to be removed from the upstream request.
`set_request_headers`	Endpoint Block, Proxy Block, Backend Block, Error Handler	Key/value(s) pairs to set request header in the upstream request.
`add_request_headers`	Endpoint Block, Proxy Block, Backend Block, Error Handler	Key/value(s) pairs to add request header to the upstream request.

All *_request_headers are executed from: endpoint, proxy, backend and error_handler.

Response Header

Couper offers three attributes to manipulate the response header fields. The header attributes can be defined unordered within the configuration file but will be executed ordered as follows:

Modifier	Contexts	Description
`remove_response_headers`	Server Block, Files Block, SPA Block, API Block, Endpoint Block, Proxy Block, Backend Block, Error Handler	List of response header to be removed from the client response.
`set_response_headers`	Server Block, Files Block, SPA Block, API Block, Endpoint Block, Proxy Block, Backend Block, Error Handler	Key/value(s) pairs to set response header in the client response.
`add_response_headers`	Server Block, Files Block, SPA Block, API Block, Endpoint Block, Proxy Block, Backend Block, Error Handler	Key/value(s) pairs to add response header to the client response.

All *_response_headers are executed from: server, files, spa, api, endpoint, proxy, backend and error_handler.

Set Response Status

The set_response_status attribute allows to modify the HTTP status code to the given value.

Modifier	Contexts	Description
`set_response_status`	Endpoint Block, Backend Block, Error Handler	HTTP status code to be set to the client response.

If the HTTP status code ist set to 204, the response body and the HTTP header field Content-Length is removed from the client response, and a warning is logged.

Parameters

Query Parameter

Couper offers three attributes to manipulate the query parameter. The query attributes can be defined unordered within the configuration file but will be executed ordered as follows:

Modifier	Contexts	Description
`remove_query_params`	Endpoint Block, Proxy Block, Backend Block, Error Handler	List of query parameters to be removed from the upstream request URL.
`set_query_params`	Endpoint Block, Proxy Block, Backend Block, Error Handler	Key/value(s) pairs to set query parameters in the upstream request URL.
`add_query_params`	Endpoint Block, Proxy Block, Backend Block, Error Handler	Key/value(s) pairs to add query parameters to the upstream request URL.

All *_query_params are executed from: endpoint, proxy, backend and error_handler.

server "my_project" {
  api {
    endpoint "/" {
      proxy {
        backend = "example"
      }
    }
  }
}

definitions {
  backend "example" {
    origin = "http://example.com"

    remove_query_params = ["a", "b"]

    set_query_params = {
      string = "string"
      multi = ["foo", "bar"]
      "${request.headers.example}" = "yes"
    }

    add_query_params = {
      noop = request.headers.noop
      null = null
      empty = ""
    }
  }
}

Form Parameter

Couper offers three attributes to manipulate the form parameter. The form attributes can be defined unordered within the configuration file but will be executed ordered as follows:

Modifier	Contexts	Description
`remove_form_params`	Endpoint Block, Proxy Block, Backend Block, Error Handler	List of form parameters to be removed from the upstream request body.
`set_form_params`	Endpoint Block, Proxy Block, Backend Block, Error Handler	Key/value(s) pairs to set form parameters in the upstream request body.
`add_form_params`	Endpoint Block, Proxy Block, Backend Block, Error Handler	Key/value(s) pairs to add form parameters to the upstream request body.

All *_form_params are executed from: endpoint, proxy, backend and error_handler.

The *_form_params apply only to requests with the POST method and the Content-Type: application/x-www-form-urlencoded HTTP header field.

server "my_project" {
  api {
    endpoint "/" {
      proxy {
        backend = "example"
      }
    }
  }
}

definitions {
  backend "example" {
    origin = "http://example.com"

    remove_form_params = ["a", "b"]

    set_form_params = {
      string = "string"
      multi = ["foo", "bar"]
      "${request.headers.example}" = "yes"
    }

    add_form_params = {
      noop = request.headers.noop
      null = null
      empty = ""
    }
  }
}

< Expressions

API >